This invention relates to an improvement of the end face of an endoscope for observations of human body cavities and occasionally for medical treatment thereof, including an outer sheath to be inserted into the body cavities and a view window of an observation system disposed at the distal end of the sheath.
Generally, in this type it be endoscope, whether of a direct-viewing rigid type with an unbendable rigid sheath or of a flexible type with a flexible sheath, the distal end of the sheath is formed roundly and smoothly. This is done for the purpose of preventing the distal end portion of the sheath from damaging tissue inside a body cavity when the sheath is inserted into the body cavity.
In one such prior art endoscope, therefore, an annular distal end edge of the sheath is rounded to preclude the possibility of damage to the tissue. Such conventional consideration may not, however, provide a fully effective measure to counter such danger yet, since the outer sheath is generally a thin pipe or tube, so that the radius of curvature of rounding on the end edge, if any, is limited.